Fire seals are used to isolate fire zones. Fire zones include any area that contains both a fuel and ignition source, such as an engine core. In such an environment, fuels, oils, or other volatile matter may ignite in connection with an ignition source. This can potentially affect the aircraft's ability to maintain safety of flight, unless adequate measures are taken to mitigate such risk and the spread of fire. Consequently, robust fire seals are often used to help form the barrier (fire-wall) required to separate such fire zones from adjacent structures. Fire proof sealing is used to mitigate fire risk.
In the context of aviation, the United States' Federal Aviation Administration (FAA) has defined fire proof sealing as being able to withstand a two-thousand degree Fahrenheit (2000° F.) flame for fifteen minutes (15 min). The sealing is frequently implemented using rubber “omega” seals or metallic “finger” seals. These seals compress when, e.g., a thrust reverser of an aircraft is closed. Design constraints that are used in the selection of a seal include a force required to compress the seal, an operating temperature of the seal, a weight of the seal, and a range of deflections that a seal can accommodate. As the size (e.g., diameter) of a seal increases, the amount of force required to compress the seal generally increases. Furthermore, larger seals are subject to an increased risk of instability (e.g., folding over) relative to smaller seals, and as a result, it might not be possible to maintain a sealing capability during exposure to direct flame and high pressure.